1. Field of the Invention
The present invention relates to an oscillator for effectively obtaining an ultrashort-pulse light utilized in a high-intensity laser system, and in particular, to an intense optical high field generator disposed within the oscillator for obtaining a wide band ultrashort-pulse light by utilizing chirped pulse amplification.
2. Description of the Related Art
In an optics field utilizing a high-intensity light, various studies have been carried out, for example, such that an intense optical high field is generated using a high-peak power light for X-ray generation or electron acceleration. The high-intensity light is considered to be utilized in the future to generate a high-intensity gamma beam in combination with an accelerator. This intense optical high field has been examined to be applied to a nuclear technology.
The inventors suggested a wide band ultrashort-pulse optical oscillator capable of effectively generating an ultrashort-pulse light with high-peak power in a wide band, as disclosed in Patent Document 1.
The wide band ultrashort-pulse optical oscillator uses a chirped pulse obtained by expanding a time width (pulse width) of a laser pulse of a laser oscillator by using a broad band spectrum. The wide band ultrashort-pulse optical oscillator includes: one or plural optical amplification media having an ability to convert optical energy for a wide band or plural bands and performing optical energy conversion into an optical pulse oscillated from an optical resonator; an energy injection unit which generates the optical energy by injecting energy to the optical amplification media or injects the optical energy to the optical amplification media; a negative dispersion element which gives negative dispersion to an oscillating optical pulse; a mode locking unit which induces a mode locking to the optical resonator; a positive dispersion element which gives positive dispersion to the oscillating optical pulse; and an optical system which is formed such that the optical pulse circulates along a loop-like optical path from the optical amplification media via the negative dispersion element, the mode locking unit, and the positive dispersion element, back to the optical amplification medium in at least one of a forward direction and a backward direction. With such a configuration, a high-intensity ultrashort-optical pulse is configured to be generated with high efficiency in the wide band.
In the nuclear technology, however, an optical beam with a better stability, a MHz-level repetition rate, a high quality, and a high intensity is required to generate a high-intensity gamma ray in combination with an accelerator.